1. Field of the Invention
This invention relates to a battery discriminating method, dry cell battery pack, and electronic device, and more particularly, is applicable to a dry cell battery pack for supplying a direct current and an electronic device in which both this dry cell battery pack and a battery pack can be used.
2. Description of the Related Art
Nowadays, high-capacity battery packs storing battery cells such as a plurality of lithium-ion battery cells has been used to supply a direct current to electronic devices such as a portable personal computer, video camera, and portable telephone.
Such battery packs contain chargeable battery cells, thus they are very expensive. However, as electronic devices become smaller in size and achieve a larger saving in power consumption, inexpensive dry cell batteries come to be used in electronic devices which could be used only with charge-battery packs, hitherto. Battery packs become unusable if the battery becomes empty when used at the place he has gone to, because they have a charging system. Accordingly, the necessity to carry a plurality of charged battery packs occurs.
However, to buy a plurality of charged battery packs is economically burdensome on the user because battery packs are expensive as described above. If electronic devices can be used with dry batteries, it is very convenient for the user since the user can buy dry batteries at a nearby store or the like and can start the use of an electronic device again.
In battery packs and dry cell battery packs usable in the same electronic devices, the structure of electrodes is the same naturally. Thus in this state, it is feared that a dry cell battery pack is fitted in a charger. Therefore, it is needed that a battery pack is made so as not to fit in a charger, or it is needed to prevent the charging that a charger discriminates that it is a dry cell battery pack if a dry cell battery pack is fitted in a charger. It is more convenient that dry cell battery packs and battery packs are discriminated not only by chargers but also in accordance with the specifications of electronic devices.
Heretofore, to discriminate battery packs from dry cell battery packs, for example, a concave part is provided on the side of a battery pack facing an electronic device but the concave part provided on the battery pack is not provided on the side of a dry cell battery pack facing the electronic device. Further, a push switch which can move up and down by means of a spring or the like is provided on a face for attaching a power source of the electronic device. When the battery pack is fitted to the electronic device, the push switch provided on the power source attaching part is connected with the concave part, so that this push switch is not pushed down. A microcomputer in the electronic device detects this state and determines that a battery pack is fitted thereto. On the other hand, when a dry cell battery pack is fitted to the electronic device, the push switch provided on the power source fitting part is pushed down by a flat part of a dry battery cell. The microcomputer in the electronic device detects this state and determines that a dry cell battery pack is fitted thereto. As the above, a plural sets of a push switch and a concave part are provided so that types of discriminatable power sources can be increased.
Recently, since microcomputers are low-cost, smart battery packs in which a microcomputer is built in a battery pack to perform communication with an electronic device appears. By using such smart battery packs, a remained capacity of the battery can be calculated correctly, and further, the quantity of charge is controlled to detect the life of battery and transmit it to an electronic device. The electronic device displays it on a display unit such as a liquid crystal panel of the electronic device.
By the way, the use of dry cell battery packs in the electronic devices which can use smart battery packs has been also considered so that electronic devices which can use both dry cell battery packs and battery packs comes to entry as described above. However, if a microcomputer is built in dry cell battery packs similar to smart battery packs, it becomes expensive; as a result, low-cost performance of dry cell battery packs, which is one of the advantages, cannot be realized.
Moreover, in the above-described method of discriminating between battery packs and dry cell battery packs, types of those packs are discriminated in the external form of battery packs and dry cell battery packs, therefore, it is needed that a push switch described above is provided on the battery fitting part of an electronic device; it suffers limitation on planning of electronic devices. Also, in the case where the reduction of the size of electronic devices is realized by providing a plurality of push switches to discriminate between plural types of batteries, a space between switches become narrow, so that error discrimination is likely to occur.